Sempiternal
by bravevulnerability
Summary: 'There are only two options: let her die, peacefully, naturally, like a human should, or save her life by damning her at the same time. ' A Castle Halloween Bash 2016 entry. Three shot.
1. Chapter 1

_sempiternal:_

 _(adj.) eternal and unchanging; everlasting._

* * *

"C-castle," she gets out through the harsh chatter of her teeth, squaring her jaw to still the violent trembling as he collides with the steel of the door for what has to be the hundredth time. "It's not going to budge."

Beckett watches him step back from their only exit, scowling at the unmoving metal, and if she could feel anything at all, she'd be impressed by the massive dents the slams of his shoulder have made in the interior, but neither his body nor her bullets have made a difference. They've been trapped in this freezer for a solid half hour and she's beginning to feel the spread of numbness through her fingers, the exposed pieces of her skin, leaching through her bones.

She knows the symptoms of hypothermia, knows the three phases – mild, moderate, and severe. And she knows where they'll soon end up on that scale at this rate.

Shockingly, Castle has yet to suffer the effects of the cold, still moving without issue, still breathing normally, still fighting. She chalks it up to his larger size, the extra body heat, hates him a little for it as she sits shivering against the wall, wishing he'd come share some of that excess warmth with her.

"Rick," she whispers, his name a labored breath falling past her lips, and he turns on his heel, his eyes shifting from a terrified midnight, dark as the night with bright strikes of worry like shooting stars, to an electric, almost unnatural blue.

"Oh Kate," he breathes, shrugging his coat off and she immediately begins to shake her head.

"No, don't," she rasps, but she gravitates towards him when he drops down beside her, seeking that wealth of heat he seems to possess. "You'll - freeze."

"I won't," he swears to her, but she still resists the drape of his coat until he's wrapping it around her, blanketing her in the extra layer of wool. Prolonging the inevitable. "I'm fine, Beckett. Promise."

"Then just - just come here," she mumbles, hooking her fingers in the front of his dress shirt, and Castle complies without hesitation, settles down on the floor next to her and bands an arm around the coiled ball of her body. "Shared body heat."

"Doesn't that require us to get naked?" he quips and her chapped lips crack into a grin against his neck.

"N-not this time, Castle," she murmurs, curling into him, sighing in relief she doesn't have the energy to hide when his arms bundle her tight against his chest.

He gasps, loud and overdramatic, and squeezes her shoulder. "We definitely have to survive this now if there's a chance at a next time."

"We'll make it. H-have to." Kate nuzzles in closer, her brow furrowing at the lack of reaction when the frozen tip of her nose touches his throat, when he fails to shiver or brace his body against the cold. "You already feel like ice."

Castle releases a quiet exhale against her temple, slips his hand inside the cocoon of his coat and rubs his palm up and down her arm to create friction, generate heat. "So do you."

"I can't feel anything," she slurs, pursing her lips, moving her tongue against her teeth, but even the cavern of her mouth feels as if it's going numb, going cold. "I - I always thought being a cop, I'd take a bullet."

"Kate," he murmurs, pressing his cheek to her forehead, adjusting the hood of her jacket over her head and trying to cover her ears.

"I never thought I'd freeze to death," she confesses, fear a subtle spark in the pit of her stomach, smothered by the slosh of ice within seconds.

"Hey, we're still here," he argues softly, the stroke of his knuckles to her cheek so smooth, not even a slight tremble in his touch, but maybe she's just imagining the grace of his movements.

It's not like she can accurately determine anything right now, the chill layering over her brain like a blanket, the frigid temperature of the freezer coating her mind in a frosty haze.

"I just wish… wish this was one of your books and you could rewrite the ending," she rasps, blinking when her eyes fall shut and forget to reopen.

She thinks he holds her tighter, attempts to burrow her body in deeper against his, but she can't tell, can barely do more than stare up at him with eyes that threaten to slide shut and stay that way. "I'm sorry, Kate."

"For what?" she asks in confusion, wishing she had the energy to snag the hand brushing her arm, cradle it to her chest.

"For being me, for going rogue, not being fast enough, letting this happen. I could have – I never should have called you, gotten you into this. I'm so sorry. This is all my fault-"

"No, Castle, shh," she soothes, reaching upwards to touch her fingers to his chin, unable to feel the skin beneath, uncertain whether or not she accomplishes her goal as her eyelids fall closed beneath the worsening weight of the cold. "We found the bomb. Just… just too late, okay?"

"I'll get you out of here," he whispers, the dull press of his lips to her forehead all she can register apart from his words. "I promise, Kate. I'll get us out-"

"Castle," she interrupts, forcing the lids of her eyes to part one last time, just once more… "Thank you. For being there."

Castle's hand closes around her fingers at his chin, touches the tips of them to his lips, and it's such an odd sensation, able to see, but unable to feel the innocent kiss to her skin.

"Always."

The corner of her mouth twitches and she musters her breath for more, words she wants to leave him with, but her heart is thudding like a dying thing against her ribs, short circuiting and turning her lungs to shards of ice that crack with every inhale.

"I just want you to know how much I…"

Her fingers trip downwards, but she doesn't know where they land, only that the cold is closing in, the darkness weighing her down, and she sinks deeper into Castle's embrace, drifts to the sound of his voice calling her name.

* * *

"Kate, hey," he calls, his desperation beginning to grow and spread like poison through his veins. "Stay with me."

He nudges her, willing her to wake, but her skin is practically blue, her body limp in his arms, and Castle cradles her cheek in his palm, touches his fingers to the dull proof of life beneath her jaw. Her pulse is waning, succumbing to the chill of the freezer, and weakening with every passing second.

"No," he whispers, holding her tighter against him, as if that will help, but he's absolutely useless to her. He can't break down the door, can't protect her from the cold or keep her alive long enough for the cavalry to ride in and save them.

He can't even offer her warmth.

"Kate, you have to wake up," he pleads softly, shifting her body in his arms. "You can't just - you're not allowed to die. Not you."

But she can't hear him, too far under, and Castle glances back towards the freezer's door, one of the few surfaces he's faced in this lifetime that he can't breach with his bare fists. He could try again, keep beating against the steel until _something_ happens, but that would mean leaving Kate's side, unable to monitor the decline of her pulse, the struggling beat of her heart drumming loud and ever present through his skull, but consistently fading. It's all fading.

The flood of her blood is beginning to slow from its usual rush beneath her flesh, the heat of it dropping quickly, her temperature threatening to match his within minutes. Her organs would fail soon, her brain function would cease, and her heart would stop, leaving him alone with the shell of the woman he loves, awaiting death without her.

He refuses to accept it.

"Come on, Kate," he urges, standing with her body still cradled against his chest. She's dead weight in his arms, unmoving, and he wracks his brain, searches through the archives for a solution, for anything other than waiting for help that may never come.

But any potential choice, any other decision, is stolen from him within minutes of pacing the ice encrusted floors, critically assessing the walls for a weakness, when he senses her heartbeat begin to stutter and die out.

Dying, she was dying.

Castle grinds his teeth to suppress his panic, dropping to his knees to lay her gently across the floor, contemplating the idea of CPR, but he's afraid he may break her ribs with the force of his chest compressions, her body too fragile for the strength of his shaking hands. He can't remember the last time in the past 200 years that his hands shook. Can't recall ever losing the careful grip of his control to the consumption of fear and desperation, imagined grief.

There are only two options: let her die, peacefully, naturally, like a human should, or save her life by damning her at the same time. Both were permanent, both detrimental in their own way, and he only wants to do right by her, do what Kate would want.

But rarely does he have any idea what Kate Beckett truly wants from him.

Castle unwraps the blanket of his coat from around her stiffening frame, feathers his hand over the center of her chest, press his fingers to the collapsing beat of her heart.

Can he really bear to live without her?

Her heart goes silent.


	2. Chapter 2

She wakes in flashes, glimpses of ice blue walls all around and eyes with a matching shade staring back at her, the darkness of the sky and the lights of the city, all smearing her waning vision before she sinks beneath the crashing waves of sleep over and over again. Voices infiltrate her hearing, his the most prominent, but others too – his daughter, frantic and concerned, his mother exasperated and uncertain, and then there is silence, long silence. But Castle never leaves, she doesn't have to be conscious to trust in that.

When her eyes peel open and remain that way, she knows hours must have passed, the sky outside the window a mélange of pale blues and brightening greys, her body no longer burning with the frigid kiss of freezing to death, no longer numbed from the chill. The back of her throat is on fire, the fierce spread of flames racing up and down her trachea, searing her tongue, and she begins to wonder if it's been more than hours, if 'days' is a more accurate estimation.

The hunger spreading through her chest aches, as if she hasn't eaten in days, and maybe her hypothermia had been so severe, she'd been hospitalized for a longer period of time than she could have imagined. But if that were the case, what about the bomb? And what about her partner, the man who had held her through the consumption of cold?

"Castle?" she croaks, scanning her surrounding with bleary eyes, realizing she's… in his bedroom?

"Kate."

Her gaze swings towards the doorway, relief momentarily overriding the hunger, the uncertainty, at the sight of him striding towards her, alive and well and not a frozen corpse.

"You're okay," she whispers, relishing in the tentative upturn of his lips, the reassurance in his gaze, but there's something wrong, a strange tension lining his features, settling atop his shoulders and straining his spine as he approaches her.

He looks grief stricken.

"So are you," he murmurs, voice rough, sounding as if he hasn't spoken in days, but his fingers graze her forehead once he reaches the bed, brushing the hair back from her face, and the ability to feel his touch after not being able it feel at all steals the majority of her focus.

"Happened?" she rasps, pushing up on one of her elbows when he takes a seat on the edge of the bed next to her hip, a strange mixture of matching relief and a foreign shade of worry swirling through the blues of his gaze. "The bomb?"

"I took care of it when we got out of the freezer," Castle assures her and she sighs, grateful, before her brow hitches.

"Wait, you - you got us out?" she manages, the itch in her throat growing unbearable, too intense to ignore for another second. "Castle, do you have water?"

"No, it wasn't me. And I do but… Kate, you aren't thirsty for water," he hedges and she stares back at him in confusion.

"My throat," she tries to explain, every swallow agony, but Castle only continues to watch her with apprehension and a heavy layer of guilt in his eyes that she just can't understand. "Please."

He startles her with how fast he stands, disappearing from the room and returning with a glass of water in mere seconds, presenting it to her with a rueful look.

Kate accepts the glass with an unsteady hand, doesn't protest when he supports the bottom of the cup with his palm to ensure its place in her fingers. She takes a long sip, savors the slide of cool liquid down her throat, but he's right, the wrenching hunger, the fiery thirst, isn't quenched.

"Castle," she mumbles, allowing him to lower the glass to the nightstand. "What happened?"

He plops back onto the bed and Beckett sits up, awaits the skill of his storytelling to be put to good use.

"After you passed out in the freezer, there was nothing I could do," he admits, his head bowed and his gaze trained on the fists of his hands in his lap. "You were fading so fast, Kate, and I - I tried everything. I couldn't let you die."

"Castle," she murmurs, reaching tentatively for his face, draping her palm to his cheek, watching his eyes fall closed. "It wasn't your fault. And I'm right here, you kept me alive-"

"No, I didn't," he chokes out, so much grief, and wraps gentle fingers around her wrist. "The one thing I could have done for you, keeping you warm, I was incapable of doing. You died and I - maybe it was selfish of me, but I couldn't let you go."

Could the cold have affected his brain?

"Rick, are you sure you're-"

"Look," he breathes, drawing her hand away from his face, lowering it to the space between them and brushing his thumb to the inside of her wrist. "Pull back the fabric of your hoodie."

Kate glances up to him, but his eyes are still closed, his lips pursed, waiting, so she sighs, does as he says and…

"What is that?" she demands, touching her own fingers to the already healed scar consuming the skin of her wrist, the curve of what appears to be a deep puncture wound branded into her flesh.

"And here," Castle continues quietly, releasing her wrist to graze two fingers to the bottom of her throat, just below her collarbone. "I - I'm so sorry, the venom - I had to spread it as quickly as possible."

Her heart begins to… well, anxiety flutters through her chest, the dull trace of panic rippling along her ribs, but her heartbeat is strangely silent.

"What are you talking about?" she whispers, following the direction of his hand, pressing her fingertips to the bare skin of her neck and feeling the raised flesh of a similarly shaped scar just shy of the swell of her breast. "Castle, what is this?"

"You're not going to believe me," he sighs and Kate shoves the cover of the blankets from her legs, swings them over the edge of the bed and staggers for a moment as she finds her footing, swaying for a handful of seconds before Castle is rising beside her, cradling her elbows to steady her.

"You haven't eaten, you're still weak," he explains and she nods, because at least that makes sense.

"The bathroom," she murmurs, shuffling them both towards the en suite. "I want to see."

His body tenses beside hers and she has no idea what's going on with him, but they'd just miraculously survived certain death in a freezer and she dismisses the odd behavior, rediscovers her balance, and stalks into the bathroom despite the dizziness, flicks on the lights.

Beckett hisses at the brightness, blinks until her vision adjusts, and proceeds to the mirror, jerking the fabric of her jacket, the t-shirt beneath, out of the way.

"What the hell happened to us?" she mumbles, assessing the crescent shaped scars decorating her skin, one just below the bone of her jaw, the other closer to her left breast, her collarbone. "You said something about venom? Did the doctors have to inject us with something?"

"There were no doctors," he replies, his voice quiet, shameful, and Kate glances up to him in the mirror. "My - Alexis and Martha rescued us an hour or so after you… died and I-"

"Why do you keep saying that?" she snaps, spinning on her heel, placing the disbelief of his story on hold to stand in front of him, meet his eyes, and reel the truth out of him. "I'm not dead. I'm right here. Unless this is some hypothermia induced dream-"

"Fuck, I wish," he scoffs, scrubbing a hand over his eyes. "You're going to be convinced it's a dream once I tell you the truth-"

"You'll never know _what_ I think if you don't shut up and actually _tell me_ the truth," she growls, snagging her fingers in the hem of his shirt, and Castle huffs.

"Fine," he mutters, yanking on the collar of his t-shirt, exposing a scar similar to hers below his collarbone. "That's a bite mark, Kate. I was bitten 204 years ago and I've been this way ever since – immortal. And now, because of me, you are too."

"Bitten?" she echoes, her mind already becoming swept up in the whirlwind of information that makes no sense. "By… what?"

"A vampire," he sighs out, attempting to take a step back from her, but she tightens her grip on his shirt, nearly rips the fabric.

"Are you insane?" she whispers, sincerely worried for him, but part of her is attempting to assemble the facts, afraid of the potential conclusion.

"Think about it. Just last night in the freezer, why didn't the cold affect me? Your body temperature dropped within minutes, Kate. You were shivering violently, hardly able to speak through it, and I was fine," he presses on and Beckett lets him go, seals her palm to her forehead. "Even after I wrapped you in my coat, the cold didn't faze me. My movements failed to slow, my speech remained even, and my temperature never dropped because it never changed. I was already cold because my body no longer possesses the ability to produce heat."

"No," she argues, pointlessly, but then Castle is grabbing her hand, holding her palm to his chest, where his heart should be.

"What do you feel?" he questions, and she may not feel anything beneath the drape of her hand to his sternum, but the heartbreak is written all over his face as she yanks her hand back.

Kate stumbles into the sink, away from him, but Castle only slumps against the wall. "You're… what did you do to me?"

"You died in my arms," he whispers, crossing his own arms over the empty cage of his ribs. "I had no right to make the decision for you, I owe you a lifetime of apologies for that, Kate. But I saved your life by turning you into one of my kind."

"Your kind? You - you actually mean a _vampire_?" she hisses, rubbing her fingers over the newly acquired scars on her upper body. "How - this doesn't make sense. They're not real, they're not… is this a dream? It can't be - it's not real. It's not - Castle?"

He straightens at the plea of his name, the leak of horror into her voice, and approaches her with hands raised in supplication. She doesn't protest when Castle touches her shoulder, traces the limb of her arm until he can claim her hand, guide it to her own chest.

"The man who turned me… I hated him," he murmurs as she digs the heel of her palm against the bones of her ribs, desperately searching for the pound of her heart, continuing to come up empty. "I killed him after I adapted, learned how to live this way, live within society. I won't blame you if you eventually feel the same towards me."

"Why would you do this?" she rasps, her hand going slack in his grasp.

Her heart is silent, stillborn.

But she imagines it would stutter, pick up speed at the soft kiss of his forehead to hers. She's lost and confused and uncertain of her current reality, but she still trusts him, no matter what happens, she trusts that Castle would never do anything that would even risk hurting her.

"Because I love you, Kate."

A broken sound leaves her mouth, a choked mixture of the grief that she now understands, that they now share, and yearning that has been repressed for far too long. Of course he loves her, enough to apparently save her life and potentially sacrifice his own sanity. But Castle cups the hard line of her jaw, shakes his head as he pulls back.

"We don't have to talk about it, about anything else for a little while, I know how… overwhelming it is, but one thing I know is that you need to drink," he explains, the mention of thirst reigniting the quieted flame consuming her throat.

"Am I… shit, Castle, if all of this is real, please tell me the blood thing isn't true?"

His lips are in a permanent frown that only deepens at the idea of disappointing her. "Sorry, Beckett. Food and water are still edible to us, but they'll never satisfy you."

Castle releases her, turns his back on her to exit the bathroom, and she hesitates for a long moment before following him through the bedroom, his office, and out towards the kitchen.

"It's going to feel strange, unnatural at first, but it'll stop the burning," he murmurs, reaching into the refrigerator, producing a cup with a lid and a straw and-

"They sell blood smoothies at Remy's?" she whispers, and he tries not to laugh, but the amusement illuminates his eyes for a split second and eases the hard knot of horror that's taken the place of her heart.

"No, no, I just - I thought it might be best to ease you into this. I had Alexis pick up your order, then I mixed it in for you."

"Alexis… she and Martha saved us?" she picks up from his explanation in the bathroom.

"Alexis is the one who figured it out. She was able to break down the door with my mother, they helped me dispose of the bomb, but they'll be out for the rest of the evening," he murmurs. "Didn't want to overwhelm you."

"Little late for that," she sighs as Castle hands her the plastic cup, but beneath the shock consuming every ounce of her being, there's a piece of her that wants to thank him for the thoughtfulness.

* * *

He watches Kate take her first sip, her nose wrinkling at the unfamiliar drench of strawberry and the underlying metallic flavor to her taste buds, but she continues to drink the smoothie, sucking at the straw until the intensity of her eyes, the ravenous shade of black bleeding from her pupils, begins to fade.

"Little better?" he inquires, attempting not to linger on how insane it feels to stand in his kitchen with her, asking her if she likes her smoothie as if they were just two normal people, as if he hadn't just upended her life.

But Kate nods, her cheeks hollowing as she takes another lengthy sip. "Will I need - this a lot?"

Castle props his hip against the kitchen counter and shakes his head. "Overall? No. But you're a newborn right now, so you'll-"

"I don't know your vampire terminology, but do not call me a _newborn_ ," she grumbles and his lips quirk into a tired smile.

He can't sleep, but he is so damn tired.

"My only point is that because you're still new to this kind of life, it's going to take you some time to adjust, to be around humans. They're literally walking containers of blood and - hungry or not - that's going to elicit the urge to feed, so you're going to need to adapt," he attempts to explain.

He had gone over all of this with Alexis when he'd turned her, had been there when his 'daughter' had saved Martha Rodgers from despair by infusing her with immortality. Not to mention he's been a writer in two different centuries, he should have all the right words by now.

But Kate is different; he doesn't know if he'll ever have enough words for her.

"You spent so much of your time around me," she whispers, her brow creasing, her mind likely cataloging every moment spent with him. "How did you not… do this sooner?"

Castle rubs at the back of his neck. "I'm used to it, to being around people. It was a little harder with you, but I never wanted this life for you, Kate. I never wanted anything but for you to be safe and if I could have prevented this-"

"Wait, wait," she murmurs, lifting a hand to quiet him, the other holding her half empty cup to her chest. "That's how you did it, saved me every single time. Every close call with a bullet, every time a suspect went too far," she begins to list, her eyes widening with each new revelation. "You nearly murdered Jerry Tyson, Hal Lockwood-"

"Beckett-"

"And the night my apartment exploded, you - you came for me and you had to push your way through burning pieces of my building-"

"Listen, we may technically be immortal and have a few advantages, but that does not mean we're indestructible. That time _hurt_ ," he recalls, rubbing at his shoulder where a flame had engulfed his flesh, left an interesting scar along his usually tough skin.

Kate steps towards him with a spark of intrigue in her eyes, visible now with her hunger fulfilled, and pulls at his shirt. "Let me see."

"Wait, no," he protests, but she's temporarily stronger than him, her physicality at its peak in this beginning stage of her transformation.

"I want to see the evidence," she explains, rolling the sleeve of his t-shirt up until the entirety of his shoulder is visible, and he flinches at the flutter of her fingers to his damaged flesh. "Oh, Castle. I had no idea it'd been this bad."

"The pain wasn't too bad," he shrugs, but her fascination remains, her fingers scaling the expanse of the healed injury. "We can still _feel_ like everyone else, but when it comes to pain, we're more resilient than typical human beings."

"How?" she murmurs, her fingers trickling down his arm, as if comparing his seared flesh to the smooth muscle of his bicep.

"I'm not an expert," he sighs. "But from what I know - thicker skin, tougher muscles, harder bones, not to mention the quicker reflexes, heightened senses-"

"Is that why I can hear _everything_?" she groans, dropping her forehead to his shoulder, and he sucks in a breath despite the lack of good it does him. A human habit he never shook. "It feels like the volume is on high."

"Like with everything else, I promise that will subside. You'll learn to control it and then you can use it to your advantage," he informs her and Kate lifts her head.

"What about Alexis? Martha? How do you live with humans when you're…" Her jaw drops at the grimace he must fail to hide. "Was Alexis - born this way?"

"What? No," he dismisses quickly. "Alexis… it was in LA in the 1940's, her mother had given her some cash, left her alone to wander the city at seventeen and she ended up… I found her in an alley, barely alive."

"You saved her too," she realizes, softly, and he's not proud of that either, but he nods.

"I wasn't going to, but she was just - crying, begging me to help her, and I knew she wouldn't survive long enough to make it to a hospital," he recalls, combing a hand through his hair at the memory, the terrified look on the girl's face, the sound of her sobs as she pleaded for him to save her life. "I holed up in LA with her until she was a little stronger, and then I took her to the beach house I've always had in the Hamptons, gave her the chance to figure out her new life."

"So the sunlight myth?"

"Just a myth," he confirms with a small chuckle.

"No sparkling either?"

"I will forever loathe the author of _Twilight_ for creating that ridiculous idea," he mutters, noticing the beginnings of a smirk flirting with the corners of her mouth before she subdues it.

"And Martha?"

"That was Alexis," he says, glancing past her shoulder to the piano that displays a family portrait of the three of them. His family, no matter what. "About a decade after I turned her. Martha Rodgers had been a Broadway star back then too, but she was in abusive relationship with one of her cast mates at the time and the man had beaten her, dumped her body at a hospital where Alexis was volunteering and well, I'm sure you can guess."

"So you became a family?" Kate concludes, the accusatory gleam her eyes had harbored in the bathroom softened into an inquisitive shimmer, the will to understand this new world he'd thrust her into.

"I love them both as if they really were my mother and daughter," he nods in affirmation. "But I swore I'd never… I saved Alexis without thinking and while I don't regret it, I never stop wondering if it was the right thing to do for her, ending her life like that."

"But… you didn't end it, you did the opposite," Kate points out, but he shakes his head.

"I trapped her in a life I couldn't even be sure she wanted. She was just a kid and I didn't even _know_ her, didn't ask her if she wanted to be seventeen forever, to be a vampire. Just like I didn't ask you," he mutters, stepping out of the kitchen, retreating towards his office, but Kate matches his pace without even trying, catches him in the doorway.

"Castle," she sighs, standing in front of him, curling her fingers at his side. "Don't get me wrong, I'm… terrified by all of this, still not sure I really believe it, or if I'm stuck in some weird interactive dream with you."

"Careful, you're starting to sound like me when I have a theory on one of our cases," he jokes, even though it falls flat, sounds hollow, but Kate musters a tiny split of her lips for him.

"But if this is my new reality, if I'm going to live for a potential eternity…" She bites down on her bottom lip, the golden hazel of her eyes roaming his face. "It might not be so bad if I'm existing with you."

Her tentative smile spreads to his lips and he laughs softly. "Well, thanks, Beckett. I'm not opposed to an eternity with you either."

She quirks her eyebrows at him, the glimmer of teasing blending with the underlying fear.

"Does this mean I'm going to have to take off of work for a while?"

"Unless you want to risk becoming one of the people you hunt on a daily basis? Probably for a couple of months," he winces, but his concern for her reaction dissipates when Kate lowers her head to his sternum, shifts to rest against him, and he knows it's because of how overwhelmed she must be, but he savors the proximity, the reassurance. "We'll come up with a believable excuse for Montgomery, for everyone, don't worry."

"I'm not worried, just – scared," she confesses, her words muffled, and Castle laces an arm around her shoulders, props his chin atop her head when she sinks into his embrace.

"Let me take you someplace safe, Kate," he murmurs, already mourning the loss of her heartbeat, a soundtrack he had grown to rely on, to love. "Just for a little while."

Her arms twine around his torso in return, her fingers twisting in his t-shirt as she nods against his chest.

"Okay."


	3. Chapter 3

The idea of spending the next eternity with Richard Castle would have horrified her once, probably would have pushed her to kill him for not letting her die in peace back when he was just a supposed asshole playboy following her around for the sake of a story that has long since been told. But while it still scares the shit out of her sometimes, the idea of forever with him wouldn't have sounded so bad before he'd saved her life that night in the freezer, and she no longer minds the prospect of it so much now either.

She'd been at risk of loving him then and she was under no illusions over the depths of her love for him now, how that love blossomed like a brilliant flower through her chest, vibrant vines twining around her ribcage, petals tickling at her stationary heart, her useless lungs.

Within these three months spent away - the "transition period", as he liked to call it - in a secluded villa on the island of Cyprus, she tends to the bloom of it, lets it grow, has stopped trying to smother it.

Though, it had taken her a while to even think about the development of her feelings for Castle, to focus on anything other than her new form of living, the foreign needs and requirements that came with being vampiric, the restrictions. To his credit, Castle proved to be an excellent teacher, patient and understanding, helping ease her into every adjustment step by step until eventually they were able to spend entire days around actual humans and the urge to taste blood on her tongue no longer overpowered her control.

"I knew your control freak tendencies would benefit you, Beckett," he'd teased her as they'd walked through a marketplace in the middle of the day and Kate had rolled her eyes, startled him with the playful nip of her teeth to his jaw.

"You're just lucky I prefer my meals in the form of smoothies these days," she'd hummed, snagging his hand and twining their fingers, meandering through the gorgeous island with him as if they were just two people simply on vacation, on the cusp of being more.

At least part of it had been true.

Hearing the thoughts of those around her, the dull murmurs of minds, insight into each and every human being within a short radius eventually helped soothe the acquired urge to attack too. Though, at first, it had driven her completely crazy, her compartmentalization skills shot to hell, but Castle had coached her through it, soothed the onslaught of thoughts in her head that weren't even her own.

Within two weeks, she's able to sort through them, shut them down if she has no desire to listen. There is one mind she's incapable of reading though, the one she wants to know more than any other.

"Powers don't usually work on… mates," he reveals one night, sitting beside her on the edge of the infinity pool beneath the blanket of midnight blue overhead, the twinkle of the stars.

Kate chokes on her own breath. "Shit-"

"Ouch, Beckett," he huffs in offense, but he laughs at her as she buries her face in her hands in embarrassment over his only logical explanation.

"Why do I even have this… what do I even call it? A special gift?" she questions, but Castle smirks in response.

"Super power," he amends, earning the light smack of her hand to his arm. "And I don't have the answer for that. From what I've learned, certain people are just reborn with them, but seriously, can you imagine once we get back to the city, to the NYPD? Interrogating suspects will be as easy as breathing."

"And avenging my mother's death… it finally feels possible," she murmurs, aware of the stiffness that invades his shoulders, climbs his spine, and Kate sways into his side. "It's not so dangerous anymore, you know that."

"We don't know that," he argues quietly. "For all we know, they could be like us, or have people like us working for them. The danger doesn't disappear just because you're less vulnerable to violence. I'm not saying I want you to give this up, just… promise me we stay partners, that I continue to have your back. That we do this together."

It's the first time she leans in, brushes her lips to his mouth in a kiss that is tender but resolute, a soft caress and a seal of certainty, a promise. A last first kiss.

"Partners, Castle. Always."

By the time their return date to New York begins to grow near, she's fallen into the habit of spending her nights in his bed – not sleeping, she had quickly learned that vampires do not possess the privilege of rest, much to her chagrin – and lying against him as the sun crests the horizon, bleeds its light onto the bed sheets, trailing warmth along her naked skin.

"Don't ever regret this," she mumbles on their final morning in Cyprus, earning the downwards tug of his brow in question, but it doesn't take him long to understand, to discover her train of thought.

"I wanted you to have the best life possible, as a human," Castle states, his reasoning unwavering, but she fits her palm to his jaw, stains her smile to his mouth.

"Castle, it wasn't until I met you that my life became extraordinary," she confesses in this moment of vulnerability, naked and tangled around him, but feeling braver than ever before. "I know it took awhile for me to admit that, but it's always been true."

"Kate-"

"I don't regret it," she whispers, shifting her body over his, easing him onto his back and straddling his hips, draping her torso atop his, aligning the dormant muscles of their hearts, the paled flesh of their scars, and cradling his face as he splays his palms over the wings of her shoulder blades. "I love you back."

He rises into the touch of her lips, devastates her mouth with a kiss that leaves her breathless, that floods electricity and heat through the cold, empty cavern of her body that never fails to come alive for him.

She arches into him when he flips them over, pinning her down to the mattress with the twine of their hands above her head, and catches his bottom lip between her teeth before she speaks one last truth, before she stops speaking altogether.

"And I wouldn't change it."

There's no one else she would rather spend the entirety of her forever with.


End file.
